This invention relates to floor and roof constructions, and more particularly, to steel joists having supports for spanner bars which are used to support form work for pouring concrete slabs in place on steel joists.
In some methods of constructing floors and roofs, steels joists which are positioned to span structural supports hold forms, such as plywood sheets, and concrete is poured on the panels to form a slab. It is desirable to be able to reuse the panels and the supporting structure for the panels after the concrete has hardened and the forms are removed. In order to reuse the panels, the forms must be supported in such a way that they can be removed with little or no damage to them, and the prior art teaches a variety of techniques and apparatus for supporting forms in such a way that they can be removed and reused. However, some of the methods and apparatus are not applicable to open web joist systems; some of which may be used with open web joist systems are difficult to use in practice; and some of the methods and apparatus may raise safety questions.
The elements which support the panels must be kept from being encased in the concrete which is poured in order to be able to reuse them. In one type of system, metal bars, referred to herein as spanner bars, extend between adjacent joists and provide support for the concrete forms. The prior art methods of supporting spanner bars at the joists, especially at open web joists, can present problems in assembly, disassembly, adjustability, adaptability to a variation of joist structures, and safety.
The spanner bars typically are supported at or near the upper chord and have support means which are adapted to cooperate with or are an integral part of the upper chord. Some of these support means require special configurations for the top chord and the support means are typically encased in concrete and hence not reusable.
It is desirable that the support for the spanner bars can be assembled and disassembled by relatively unskilled labor using only simple tools. In handling heavy members of structural steel, workers usually wear gloves, and it is desirable that a minimum of care and little manual dexterity be needed to assemble and disassemble the elements of the support apparatus.